Supplementary material Macrofauna communities across a seascape of seagrass meadows: environmental drivers, biodiversity patterns and conservation implications

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Supplementary material

Macrofauna communities across a seascape of seagrass meadows:

environmental drivers, biodiversity patterns and conservation implications

Iván F. Rodil^1,2,*, Andrew M. Lohrer³, Karl M. Attard^2,4, Judi E. Hewitt^3,5, Simon F.

Thrush⁶, Alf Norkko^2,7

1Departamento de Biología, Instituto Universitario de Investigación Marina (INMAR), University of Cádiz, Spain.

2Tvärminne Zoological Station, University of Helsinki, Hanko, Finland

3National Institute of Water & Atmospheric Research, Hamilton, New Zealand

4Department of Biology, University of Southern Denmark, Odense, Denmark

5Department of Statistics, University of Auckland, Auckland, New Zealand

6Institute of Marine Science, University of Auckland, Auckland, New Zealand

7Baltic Sea Centre, Stockholm University, Stockholm, Sweden

*Corresponding author; e-mail: ivan.franco@uca.es; ivan.rodil@helsinki.fi

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Figure S1. Schematic illustration of the biodiversity sampling area (modified from Rodil et al.

2019) displaying 8 equal wedge-sections for community characterization across meadow sites.

Quantitative random samples (n = 16 total per site) were randomly taken per each of the wedge sections (two replicate samples per section: one in the inner 0-3 m area, and another in the outer 3-5 m area) of the main benthic organisms (macrofauna and macrophytes) were collected (i.e. 8 inner + 8 outer total samples). Random samples (n = 6 total per sites, 3 + 3) were taken for sedimentary characteristics (see Methods).

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Figure S2. Principal component analysis (PCA) showing the relationship between the best suite of sedimentary variables (BEST correlation = 0.746 for chlorophyll a, organic matter, 125, 250 and 500 µm) and the distribution of meadow sites with all the replicates (top panel) and average values (bottom panel).

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Figure S3. Mean (±SE) values of the main sedimentary variables across the meadow sites with respect to an increasing spatial gradient of shoot density (see Figure 2A). The sites in the x-axis are arranged by increasing spatial gradient of shoot density. Sites TS0, TSf, T1 and T2 are located in the more sheltered inner area (left from the dashed red line) along the Hanko peninsula (see Figure 1).

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T8 T5 T6 T7 T9 T1T2

T10 T4 T3 TS0TSf

PC1&2: 67 %

-5 0 5 10

PC1 -5

0 5

Rmar Spect Zannich

Zmar

Figure S4. Principal component analysis (PCA) showing the spatial distribution of the seagrass meadows according to the abundance of the most dominant plant species (i.e. Zostera marina, Ruppia maritima, Zannichellia spp and Stuckenia pectinata).

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Figure S5. Relationships between macrofauna community diversity descriptors and total plant biomass (see Figure 5). No significant relationship between Pielou index (J') and total biomass.

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Figure S6. DistLM plots showing (A) the total contribution (ΣR²) and (B) the mean contribution (R²±SE) of the main sedimentary (chlorophyll a, phaeopigments, mean grain size, < 63 µm), seagrass (above- and below- ground dry mass and canopy height) and algal predictors (filamentous algal biomass and abundance of Chorda filum) on the macrofauna community (i.e., abundance and ash free dry mass of the epifauna and infauna, number of taxa, Shannon diversity and macrofauna assemblages).

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Table S1. Study sites and average values (standard error) of the main environmental and sedimentary characteristics. Depth (m), temperature, organic matter (%) chlorophyll a and phaeopigments (µg/g) and mean grain size (µm).

*Sites are presented in spatial order from (inner more sheltered sites) East to (outer more exposed sites) West (see Figure 1).

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Table S2. Pearson correlation coefficients (using rcorr function in R) among sedimentary (OM:

organic matter, Chl a: chlorophyll a, Phaeo: phaeopigments, <63 µm and >250 µm grain sizes and MGS: mean grain size) and macrophyte (Shoot: shoot density, AGDM: above and BGDM: below ground dry mass, DM: total dry mass, Hmax: canopy height, Algae: algal biomass and Chorda:

Chorda filum abundance) predictors. Significant correlations in bold and italics (^*p < 0.05, ^**p <

0.01, ^***p < 0.001).

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Table S3. Grain size data, depth (0–10 cm) averaged % dry weight of each fraction at the sampling sites.

Fraction

Sites 2mm 1mm 500 µm 250 µm 125 µm 63 µm <63 µm ≥ 250

T1 1.3 1.9 14.6 36.4 35.7 8.7 1.4 54.5

TS0 1.6 0.6 3.4 44.9 44.6 2.8 2.0 50.5

TSf 1.6 0.7 3.2 46.9 43.0 2.4 2.2 52.4

T2 1.2 0.4 4.1 56.2 34.1 2.3 1.8 61.8

T3 1.0 1.0 47.8 37.4 10.5 1.3 0.9 87.2

T4 6.0 3.7 30.1 45.6 10.0 3.3 1.4 85.3

T5 14.2 10.2 32.1 33.2 7.8 1.8 0.7 89.7

T6 0.4 3.7 21.8 62.8 10.2 0.9 0.3 88.7

T7 6.4 5.4 29.8 38.4 16.7 2.4 1.2 79.9

T8 0.1 0.5 4.4 16.8 69.3 8.5 0.5 21.7

T9 1.2 2.4 13.6 39.2 31.6 11.2 0.8 56.5

T10 1.1 3.1 17.6 31.5 37.9 7.9 0.9 53.3

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Table S4. Results of PERMANOVA on the main macrophyte community attributes (i.e. Shoots:

shoot density, AGDM: above- and BGDM: below ground dry mass, Hmax: canopy height, H':

Shannon diversity index, and Algae: drifting algal biomass). Site was a random factor. Permutation (4999) of residuals under unrestricted permutation of raw data (SS Type III) were based on Euclidean distances.

Macrophyte community Source df SS MS pseudo-F p

Shoots^a Site 11 49.7 4.5 4.8 < 0.001

Residuals 180 171.0 0.9 - -

AGDM^a Site 11 29.9 2.7 4.0 < 0.001

Residuals 180 123.4 0.7 - -

BGDM^a Site 11 27.6 2.5 2.8 < 0.01

Residuals 180 2.5 0.9 - -

Hmaxa Site 11 27.6 2.5 6.8 < 0.001

Residuals 180 66.3 0.4 - -

H'-Shannon^b Site 11 18.7 1.7 15.9 < 0.001

Residuals 180 19.2 0.1 - -

Algae^b Site 11 166.3 15.1 42.5 < 0.001

Residuals 180 64.1 0.4 - -

alog(x+1) transformed

b4th-root transformed

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Table S5. Mean (SE) values of the main seagrass community descriptors. Shoot density (individuals m^-2), above and below ground dry mass (g m^-2), canopy height (Hmax, cm), Shannon diversity index (H'-Shannon), and the total number of species.

Seagrass community descriptors

Site ShootD AGDM BGDM Hmax H'-Shannon Total species^* T1 399(55) 38.9(7.4) 19.7(4.5) 19.7(1.6) 0.80(0.15) 6 TS0 266(37) 40.8(4.7) 18.3(3.2) 24.1(2.2) 0.85(0.11) 6 TSf 218(30) 43.0(5.7) 12.5(2.0) 31.4(1.6) 0.83(0.11) 6 T2 384(59) 50.9(5.5) 18.2(2.6) 27.5(3.2) 0.76 (0.09) 6 T3 738(39) 111.1(7.9) 34.1(2.9) 37.5(2.9) 0.46(0.10) 6 T4 636(78) 55.9(7.3) 16.4(1.9) 22.3(1.9) 0.1(0.06) 4 T5 406(38) 37.9(5.2) 8.3(1.7) 22.3(1.6) 1.08(0.09) 6 T6 1127(139) 73.1(14.0) 32.1(6.5) 13.1(1.1) 1.24(0.1) 6 T7 698(79) 76.1(8.5) 26.9(3.9) 24.0(2.4) 0.04(0.04) 2 T8 1117(108) 85.4(16.4) 15.8(2.0) 10.9(1.9) 1.28(0.06) 5 T9 466(59) 81.2(10.6) 23.3(5.5) 31.5(2.5) 0.53(0.09) 3 T10 754(81) 90.8(10.6) 23.6(5.5) 35.3(3.0) 0.73(0.06) 4

*Check supplementary Table S6 for a plant species description

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Table S6. The mean abundance, biomass and canopy height of the main plant species across the study sites. The abundance (individuals m^-2) of the macroalgae Chorda filum is also shown.

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Table S7. Species list composition, relative biomass (% share), and total biomass (g dry mass m^-2) of the different species comprising the drifting ephemeral algal mat (annual species). TSf showed no quantifiable algal biomass during sampling.Species name status and author attribution from World Register of Marine Species (WoRMS).

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Table S8. Mean (SE) values of the main macrofauna community descriptors. Epifauna and infauna abundance (individuals m^-2), ash free dry mass (g m^-2), mean number of taxa richness (SR), total number of taxa (TS), Shannon (H'), Pielou (J') and Simpson (1-λ) diversity indices.

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Table S9. List of the macroinvertebrate taxa (and feeding habits) sampled across sites. Species name status and author attributions from World Register of Marine Species (WoRMS). Feeding habit: detritivore, omnivore, grazer, carnivore, scavenger, and parasite.

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Table S10. Contribution, average abundance and average similarity (%) of the main macroinvertebrate taxa to the similarity (70.0 % cut-off; one-way SIMPER) of each site (average similarity within site in brackets).

Site Taxa Abund Simil Contrib

T1 (56.8)

Peringia ulvae 6.25 12.73 22.41

M. trossulus 5.01 9.09 16.00

Marenzelleria spp 3.68 5.66 9.97

M. balthica 3.77 5.51 9.70

P. antipodarum 3.67 5.27 9.28

C. glaucum 2.31 3.36 5.91

Total 73.27

TS0 (63.4)

M. balthica 6.90 15.91 25.11

P. antipodarum 5.46 10.27 16.22

Chironomus spp 3.70 8.03 12.67

Peringia ulvae 3.32 5.82 9.19

Total 73.42

TSf (60.1)

Peringia ulvae 5.99 14.89 24.78

M. balthica 4.86 10.81 17.98

M. trossulus 4.53 10.62 17.66

P. antipodarum 4.54 7.97 13.27

Total 73.69

T2 (62.9)

M. balthica 7.10 14.70 23.39

P. antipodarum 6.87 13.20 21.00

M. trossulus 2.95 4.80 7.63

Oligochaeta 3.53 3.69 5.86

73.10

T3 (69.3)

Peringia ulvae 7.87 10.21 14.73

M. balthica 7.94 9.80 14.14

H. diversicolor 7.03 9.57 13.82

R. peregra 4.40 5.78 8.34

Gammarus spp 4.00 4.88 7.04

Jaera spp 3.49 4.29 6.19

Chironomidae 3.43 4.28 6.18

70.44 T4 (70.5) Peringia ulvae 7.89 11.57 16.42

M. balthica 7.26 10.98 15.58

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Gammarus spp 5.89 8.82 12.51

H. diversicolor 5.47 7.66 10.87

Oligochaeta 5.18 5.99 8.50

T. fluviatilis 4.56 5.83 8.28

72.16

T5 (75.4)

Peringia ulvae 9.26 13.39 17.77

I. chelipes 7.07 10.15 13.46

Gammarus spp 7.01 9.88 13.12

M. balthica 6.63 9.49 12.59

H. diversicolor 5.45 7.39 9.81

T. fluviatilis 4.94 6.44 8.55

75.30

Site Taxa Abund Simil Contrib

T6 (67.7)

I. chelipes 7.23 10.01 14.78

Gammarus spp 5.90 7.99 11.80

M. balthica 5.52 7.22 10.66

I. balthica 3.40 4.07 6.01

Jaera spp 3.23 3.64 5.37

U. crassipes 3.54 3.62 5.35

P. hauniense 3.12 3.20 4.72

Hydroptila spp 3.55 3.08 4.55

R. peregra 2.61 2.96 4.38

Total 72.96

T7 (68.1)

Peringia ulvae 8.86 12.14 17.83

M. balthica 6.98 9.32 13.70

Gammarus spp 5.20 7.42 10.91

I. chelipes 4.68 5.99 8.81

U. crassipes 4.23 5.23 7.69

M. trossulus 4.50 5.22 7.67

Total 71.85

T8 (68.5)

I. chelipes 6.05 9.63 14.06

M. balthica 6.33 9.11 13.31

Gammarus spp 5.22 7.67 11.20

M. trossulus 4.36 6.43 9.39

Peringia ulvae. 4.54 5.66 8.27

R. peregra 3.60 5.39 7.88

C. glaucum 3.85 4.17 6.09

Total 70.20

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T9 (72.0)

M. balthica 8.33 11.90 16.53

Gammarus spp 6.55 8.65 12.02

M. trossulus 5.77 7.29 10.12

R. peregra 4.14 5.89 8.18

H. diversicolor 4.35 5.21 7.24

I. chelipes 3.95 5.15 7.15

Total 76.40

T10

(72.8)

M. balthica 7.76 10.56 14.51

I. chelipes 6.28 8.82 12.13

Gammarus spp 6.30 8.67 11.91

M. trossulus 6.48 8.49 11.66

T. fluviatilis 4.61 6.26 8.61

Total 75.40

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Table S11. Average Bray-Curtis dissimilarity (%) of the macroinvertebrate community taxa among sites based on SIMPER results.

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Table S12. Results of PERMANOVA on the main macrofauna community attributes. Site was a random factor. Permutation (4999) of residuals under unrestricted permutation of raw data (SS Type III) were based on Euclidean distances.

Variables Source df SS MS pseudo-F p

Total abundance Site 11 32.7 3.0 12.6 < 0.001

Residuals 180 42.4 0.2 - -

AbundEpif

Site 11 96.9 8.8 12.7 < 0.001

Residuals 180 125.1 0.7 - -

AbundInf

Site 11 43.8 4.0 10.0 < 0.001

Residuals 180 72.1 0.4 - -

Total AFDM Site 11 54.8 5.0 16.7 < 0.001

Residuals 180 53.8 0.3 - -

AFDMEpif

Site 11 18.7 1.7 17.3 < 0.001

Residuals 180 17.6 0.1 - -

AFDMInf

Site 11 55.5 5.0 13.8 < 0.001

Residuals 180 66.2 0.4 - -

SR Site 11 4.9 0.5 14.4 < 0.001

Residuals 180 5.6 0.0 - -

H'-Shannon Site 11 0.5 0.05 13.5 < 0.001

Residuals 180 0.6 0.003 - -

J' Site 11 0.0 0.0 7.1 < 0.001

Residuals 180 0.0 0.0 - -

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1-λ Site 11 0.01 0.00 10.4 < 0.001

Residuals 180 0.02 0.00 - -

All data was log(x+1) transformed. 4999 unrestricted permutations based on Euclidean distances.